Generally, a sputtering apparatus is used to deposit a target material on a substrate by accelerating ions using plasma and allowing the ions to collide with a target formed of the target material.
A sputtering process using a sputtering apparatus has an advantage of forming a thin film at a relatively low temperature of about 400° C. as compared with a chemical deposition process performed at a relatively high temperature.
The sputtering apparatus includes a target unit and a substrate unit that are provided in a chamber. The target unit and the substrate unit are respectively connected to a cathode and an anode. When a direct current power is applied to the cathode and the anode while generating a high frequency, electrons are emitted from a target of the target unit by an electric field and accelerated toward the anode.
At this point, the accelerated electrons collide with inert gas supplied into the chamber, thereby ionizing the gas. Cations of the inert gas collide with the target connected to the cathode by the electric field to realize the sputtering phenomenon by which the atoms are separated from the surface of the target.
Meanwhile, the electrons emitted from the target and accelerated toward the anode collide with neutral atoms to be excited and generate plasma. The plasma is maintained as far as the outer electric potential is maintained and the electrons are continuously generated. The separated target atoms are deposited on the substrate to form the thin film on the substrate.
FIG. 1 is a schematic sectional view of a related art sputtering apparatus.
Referring to FIG. 1, a related art sputtering apparatus includes a substrate unit SP, a target unit TP and a mask unit MP.
The target unit TP includes a rear plate 14 and a target 12. A magnet 18 may be disposed in rear of the rear plate 14. The magnet 18 forms a magnetic field to prevent electrons generated from plasma from straying off from a desired region. The target 12 that is a deposition material is fixed on the rear plate 14. A cathode (not shown) is provided between the target 12 and the rear plate 14.
The substrate unit SP includes a substrate 8 on which the deposition material will be deposited and a susceptor 10 supporting the substrate 8. An anode plate (not shown) is provided between the substrate 8 and the susceptor 10.
The mask unit MP includes a mask 2, a floating mask 4 and an insulation member 6 interposed between the mask 2 and the floating mask 4. The mask unit MP prevents the target material from being deposited on a non-deposition portion of the substrate 8. The mask 2 is formed in a rectangular frame shape and of a conductive material such as aluminum to generate plasma by maintaining an electric potential difference from the target 12 functioning as a cathode electrode. The floating mask 4 is formed of a conductive material such as Al. The floating mask 4 is disposed inside the frame of the mask 2 and electrically insulated from the mask 2 by the insulation member 6.
In order to perform a sputtering process in a sputtering chamber, an inert gas must be supplied into the sputtering chamber. In the sputtering apparatus of FIG. 1, the inert gas is supplied through an inert gas supply port.
That is, the inert gas supply port is independently provided below the chamber to supply the inert gas into the chamber. The concentration of the inert gas is gradually lowered toward a central portion of the substrate as the area of the substrate increase.
Therefore, the concentration of the plasma generated at a region close to the inert gas supply port may be different from that of the plasma generated at a region far from the inert gas supply port. In some case, there may be a region where the plasma is not generated.
In the regions where the concentration of the plasma is lower or the plasma is not generated, the cations of the inert gas collide by an electric field with the target connected to a cathode. However, the energy is too low to separate the target atoms from the surface of the target. That is, the sputtering is not normally realized.
Therefore, the substrate on which the target material will be deposited is large, a region where the plasma is not generated is created at the chamber region between the target and the substrate, thereby varying the property of a film deposited on the substrate.
Furthermore, as the substrate is large, a composition of the material deposited on the substrate is not uniform.